1. Field of the Invention
This invention relates to an electro-slag welding method, and more particularly, to an electro-slag welding method using as an electrode a steel strip in place of the usual steel wire, and also using an insulating material prepared by adding deoxidizing agent and alloying agent to a slag-forming agent, which materials permit welding of a narrow gap. The invention also relates to the electro-slag welding material used in the method.
2. The Prior Art
As a method of high efficiency welding of very thick steel plates vertically positioned, there is known an electro-slag welding method of consumable nozzle type using a steel wire. This method, however, has a drawback in that any reduction in the quantity of the welding material from the standpoint of bettering the efficiency would lead to insufficient penetration in the vicinity of the surface of the plates being welded.
FIG. 1 outlines this conventional electro-slag welding method, in which a steel tube having an outer covering of an electric insulating material consisting of a component similar to the weld slag is disposed in the center of the welding gap and a steel wire is continuously supplied through the steel tube for electro-slag welding. FIG. 1a is a plan view, and FIG. 1b is a longitudinal sectional view. As shown in the Figures, the materials 1 to be welded, for instance steel plates, are disposed in vertical positions or like, and copper shoes or shoes of like metal 3 serving as consumable material are disposed on opposite sides of the gap 2, thus forming a mold-like structure. Then, a steel tube 5 (commonly termed a consumable nozzle) covered with an electric insulating material 4 consisting of a component similar to the welding slag, is disposed in the center of the welding gap 2, and a steel wire 6 is continuously supplied through the steel tube while passing curent through the molten slag 7 to melt the continuously supplied steel wire 6 through the heat generated by the electrical resistance, the molten material being progressively solidified from lower portions to achieve the welding. In FIG. 1b numeral 8 designates the molten metal, and numeral 9 the solidified metal (welding metal).
In this method, the edge preparation is simple, the welding set-up is simplified, and the welding operation is easy. Also, the welding can be done with a single layer. Further, reducing the welding gap in this method is advantageous with respect to economy in the quantity of steel wire required to fill the gap, i.e., it can be reduced, and it is also advantageous from the standpoint of efficiency, since the welding speed can be increased.
However, if the gap is made too small, the temperature gradient at the time of welding becomes large, so that loss of thermal balance between the direction of the gap and the direction of the thickness of the plate is likely to result, thus giving rise to the drawback of insufficient penetration in the vicinity of the plate surface due to insufficient heat. This tendency becomes more prominent with increase in the thickness of the plate. As a method of overcoming this drawback, it may be thought to vibrate the consumable nozzle in the direction of the plate thickness. Such a method, however, requires a vibrating mechanism, and the convenience peculiar to the instant invention is lost.